This invention relates generally to tape cartridge loader mechanisms, for example, for loading of single-reel magnetic tape cartridges into appropriate tape drives. One specific aspect of the invention relates to load balancing to offset magnetic clutch action so as to separate a tape cartridge from a tape drive. Another specific aspect of the invention relates to cam and cam follower designs for such loaders, to efficiently lift the cartridge from engagement with the tape drive motor gear.
Computers utilize a variety of magnetic media devices for the storage of software programs and data. Information recorded on the magnetic medium takes the form of flux transitions that represent the binary xe2x80x9c1""sxe2x80x9d and xe2x80x9c0""sxe2x80x9d that form the digital information. Tape cartridges, such as single-reel tape cartridges, are commonly used in library or other archival data storage applications. In such applications, a user or a robotic mechanism selects a tape cartridge for processing and inserts the cartridge into a tape drive coupled to a computer. In a fully automated system, a mechanism within the tape drive loads the tape from its entry point to a position in which the tape becomes accessible for read-from and write-to operations.
A variety of different size data tape cartridges are available. The drives for the different size cartridges, however, must be substantially the same size, so as to fit within a standard size slot or space available within the framework of a personal computer or the like. Larger cartridges enable storage of more data on the tape within, however, the larger the cartridge the more difficult it is to design a drive mechanism to fit within the design envelope.
For example, some single reel cartridges are 105.4 mm wide, by 102 mm long by 21.5 mm high. Such a cartridge, by itself fills a substantial portion of the design envelope for the tape drive. As a result, tape drives for this type of cartridge have utilized manual loading mechanisms. All movement and operations to load the tape cartridge into the drive, open the tape door for access to the tape leader and engage the tape drive gear to the drive motor gear have been manual in nature. A portion of the cartridge remains outside the drive, even in the fully loaded position.
Data cartridge tape drives have been developed with automatic or xe2x80x9csoftxe2x80x9d loading and unloading of the cartridge. However, because of the size and complexity of the loading mechanism, these automatic loaders have been used only in drives for smaller tape cartridges.
Also, automatic cartridge tape drives must be able to load and unload cartridges many times without jamming or other failures. A failure of an automatic loader mechanism may damage a tape cartridge and makes the drive unusable until repaired or replaced. Typical design parameters for drives available today call for the loader mechanism to continue to operate successfully for at least 300,000 loading/unloading cycles. For applications with frequent cartridge replacement, such as tape library systems providing access to volumes of data to many users via networks, to have a truly useful life each tape loader mechanism must operate successfully with little or no wear for many more cycles than even this design parameter.
Automatic loader mechanisms have been developed in the past that include some form of conveyor and/or shuttle mechanism to retract the cartridge entirely within the drive and lower the cartridge for engagement with the tape drive motor gear. These mechanisms are motor driven. Many cartridge tape drives use a magnet and a metal plate to form a magnetic clutch, to engage the cartridge gear to the drive gear associated with the motor. The loader motor must supply sufficient torque during unloading to overcome the magnetic clutch forces, in order to separate the cartridge from the cartridge drive motor. This imposes a high power requirement on the loader motor. To produce adequate torque typically requires a larger motor and more electrical power. The high torque also tends to wear out drive linkages quickly.
It should, therefore, be appreciated that a need exists for an automatic loading mechanism for data tape cartridges that takes up the minimum amount of space within the design envelope of the tape drive, to allow the mechanism and the drive to handle as large a cartridge as possible. Also, a need exists for a loader mechanism of this type that is particularly durable and can operate successfully for a large number of loading/unloading cycles without any jams or other failures. To meet these general needs there is a specific need for a technique to reduce the torque requirement on the loader motor needed to separate the magnetic clutch elements, to allow use of a smaller motor and reduce stress and wear on loader components.
The present invention meets the above-stated needs and overcomes the problems with prior cartridge loader systems.
The present invention relates to a loader, for automatically loading a tape cartridge into a tape drive, preferably for reading and writing data on a tape within the cartridge. The loader includes a cartridge shuttle. The shuttle receives the tape cartridge and moves to and from a position within the tape drive in which the cartridge is operatively loaded into the tape drive. The loader also includes means for producing a force to assist in separating the gear within the tape cartridge from the gear coupled to the drive motor.
The assist force may be provided by one or more load balancing springs. In addition or alternatively, the assist force may be generated by a unique cam and follower arrangement, which applies different forces on opposing sides of the shuttle at least during initial unloading motion of the cartridge.
Thus, one aspect of the present invention relates to an automatic tape cartridge loader. The inventive loader includes a shuttle for receiving the tape cartridge and means for moving the shuttle. The movement means automatically moves the shuttle to and from a position within the loader, in which a gear within the tape cartridge engages a gear coupled to a drive motor of the tape drive. In the preferred embodiments, magnetic attraction between the gears draws the two gears into secure engagement. In this aspect of the invention, the loader also includes at least one spring. The spring produces a force opposing movement of the shuttle to the cartridge-loaded position. The spring assists in movement of the shuttle from that position, during unloading, in such manner as to assist in separating the gear within the tape cartridge from the gear coupled to the drive motor. For example, when there is magnetic attraction between the gears, the spring force helps to overcome the magnetic clutch engagement between the two gears.
In the preferred embodiment, the spring actually comprises two more springs. Although a variety of arrangements are possible, the springs typically are compression springs attached to a base, for compression by the cartridge or shuttle as the shuttle moves to the cartridge-loaded position within the loader and tape drive.
The load balancing spring forces on the cartridge shuttle help to overcome the magnetic attraction and separate the gears. This reduces the torque and/or power requirement on the loader motor during the unloading operation. The loader may use a smaller motor, and the reduced torque tends to extend the useful life of the loader and motor.
The preferred embodiment of the shuttle includes cantilevered springs for applying spring force toward the tape drive motor to the cartridge within the shuttle and for buffering the cartridge within the shuttle. The cam profiles induce motion of the shuttle slightly past the cartridge-loaded position, to produce a gap between a surface of the cartridge and an adjacent surface of the shuttle. The cantilevered springs buffer the cartridge within the shuttle, when the shuttle moves past the cartridge-loaded position. Another aspect of the invention relates to a tape cartridge loader. The loader includes a conveyor and a shuttle for receiving the tape cartridge. The conveyor is mounted for linear motion. The conveyor has two sidewalls and at least one cam profile in each sidewall. The loader includes a first cam follower bearing attached to a side of the shuttle for engagement with the first cam profile and a second cam follower bearing attached to the opposite side of the shuttle for engagement with the second cam profile. The second cam follower bearing is larger than the first cam follower bearing. The first and second cam profiles are contoured so that interaction of the bearings with the first and second cam profiles during unloading of the tape cartridge from the loader provides different forces on opposing sides of the tape cartridge.
The differing forces on opposite sides of the shuttle preferably cause a lift of the cartridge that is uneven. The forces may initiate lift of each side of the shuttle and thus the cartridge at different times during the unloading operation and may result in a slight skew of the cartridge with respect the plane of the motor drive gear. For example, in a preferred embodiment, the first and second cam profiles are contoured such that motion of the conveyor during unloading causes the first cam profile to apply force through the first cam follower bearing prior to the second cam profile applying force through the second cam follower bearing. The plane of the gear in the tape cartridge rises at an angle with respect to the plane of the drive motor gear, instead of parallel. In a tape drive having a magnetic attraction between the tape motor drive gear and the gear within the tape cartridge, these differences in the application of force on the sides of the cartridge help to overcome the magnetic attraction and separate the gears. This reduces the torque and/or power requirement on the loader motor during the unloading operation. The loader may use a smaller motor, and the reduced torque tends to extend the useful life of the loader and motor.
In the preferred embodiment, the loader also includes a frame housing. The conveyor is mounted for linear motion within the frame housing, for example by means of follower bearings attached to the conveyor that ride in one or more linear grooves in the walls of the frame housing. The frame housing may have a path constraint groove, with a first section parallel to the linear motion of the conveyor and a second section perpendicular to the first section. One of the cam follower bearings attached to the shuttle also interacts with the path constraint groove, to limit motion of the shuttle to a path defined by the path constraint groove formed in the frame housing.
In a fully automated implementation, the tape cartridge loader would also include an actuator system. This system preferably includes a rotatable actuator arm coupled to the frame housing, for inducing the linear motion of the conveyor. A motor is coupled to the actuator, for example through worm and sector gears, to drive the rotation of the actuator arm in response to a drive signal.
Another aspect of the invention relates to a tape drive incorporating the inventive cartridge loader. The tape drive includes a tape drive motor and a tape drive gear coupled for rotation by the tape drive motor. A magnet is secured to the tape drive gear for magnetically attracting a gear within the tape cartridge. The drive also includes an automatic loader, for loading the tape cartridge such that the tape drive gear engages the gear within the tape cartridge and for unloading the tape cartridge from engagement and from the tape drive.
In this aspect of the invention, the automatic loader includes a frame housing, a conveyor and a shuttle. The conveyor is mounted in the frame housing for linear motion back and forth during loading and unloading of the tape cartridge. The conveyor has sidewalls, with at least one groove formed in each sidewall. Each of these grooves has a cam profile for use in a cartridge loading operation and a cam profile for use in a cartridge loading operation. An actuator, preferably in the form of a flat rotatable arm, is coupled to the conveyor. The actuator is automatically driven so as to induce the various linear motions of the conveyor.
A first cam follower bearing, attached to a first side of the shuttle, engages the cam profiles of the first groove, and a second cam follower bearing, attached to the opposite side of the shuttle, engages the cam profiles of the second groove. The loading cam profiles of the two grooves are contoured so that interaction with the follower bearings, during tape loading, induces a motion of the shuttle for retracting the tape cartridge into the frame housing and into engagement.
The second cam follower bearing is larger than the first cam follower bearing. Also, the unloading cam profiles of the grooves are specially contoured. As a result, the interaction of the followers with the unloading profiles during unloading provides different forces on opposing sides of the tape cartridge. The differing forces on opposite sides of the shuttle assist in separation of the gear within the tape cartridge from engagement with the tape drive gear.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.